This invention relates to a gas turbine system in which a high temperature moving blade and a high temperature stationary blade of a gas turbine are steam cooled.
FIG. 2 is a schematic system diagram of a conventional general gas turbine and a bottoming cycle.
A high temperature moving blade and a high temperature stationary blade of a gas turbine 51 are cooled with bleed air 53 from a compressor 52. A system in which steam from a bottoming cycle is used for cooling of a moving blade and/or a stationary blade of a gas turbine and returned again to the bottoming cycle has not bee put to practical use.
Outlet steam from a high pressure turbine 54 of a bottoming cycle totally enters a reheater 55, where it is heated to an appropriate temperature and supplied to an intermediate pressure turbine. A system with this constitution achieves a high efficiency.
In the drawing, a zone enclosed with a one-dot chain line represents a bottoming cycle, in which the numeral 56 denotes an intermediate pressure turbine, 57 a low pressure turbine, 58 a condenser, 59 a feed water pump, and 60 an exhaust gas boiler.
With the existing equipment, as noted above, cooling of the gas turbine is usually performed with air. Recently, however, the idea of using steam from the bottoming cycle for cooling of the gas turbine instead of air cooling has been introduced in accordance with the high temperature operation of the gas turbine.
As described above, steam cooling methods for the gas turbine have been introduced here and there. However, all of these methods are still at a trial-and-error stage, and involve many unresolved issues in order to emerge as actual machines.
Take, as an example, a steam cooled gas turbine system in which a moving blade or a stationary blade of a gas turbine is cooled with steam supplied from the bottoming cycle side, and this steam is recovered and returned again to the bottoming side for an improvement in efficiency or output. In this system, a considerable amount of steam that has so far flowed in the bottoming flows into the gas turbine during movement between the gas turbine and the bottoming cycle. Thus, a marked influence is exerted on each other.